A mobile terminal is a terminal freely usable while moving without regard to places. As a representative mobile terminal, there is a cellular phone or the like mobile communication terminal, a personal digital assistant (PDA), etc. Therefore, the term ‘mobile terminal’ involves the PDA, the cellular phone, etc., but the following descriptions will be limited to the PDA for the convenience of explanation.
In complicated and diversified society, individuals each have felt the need to store and keep personal information in his/her own ways, and thus various products have been launched in the market so as to meet the personal needs. One of them is the PDA. The PDA is also called a pocket computer, which is a generic term for palm-sized small devices having calculation, information storage and searching functions for personal or business use. Occasionally, it has been mostly used in maintaining information about a schedule calendar, an address book, etc.
In particular, an industrial PDA has currently been mainly used in the distribution industry, but its market has been gradually spread. The industrial PDA refers to a PDA having various office functions, such as a barcode scanner, a credit card machine, etc. not present in a general PDA. If the industrial PDA is used, it is advantageous to efficiently progress delivery, data management, related business, etc. For example, an insurance broker of an insurance company can directly process various insurance-related tasks such as customer information management, customer searching, scheduling, a daily record of consultation, memorial day searching, funds statement processing, etc. on the spot through the PDA; a medical worker of a hospital can input or search X-ray image and graphic data as well as medical records and history of a patient, and a prescription through the industrial PDA without being constrained by time and places; and a traffic or patrol cop of the police can perform a crackdown outside of the office through the industrial PDA so that a fine levied for violation of the traffic regulations, the payment of which is currently possible after a lapse of 2 or 3 days from the crackdown, can be directly paid to banking facilities, and it is thus possible for the traffic or patrol cop to remarkably reduce a time taken in the crackdown outside of the office.
As used in various industrial fields, the industrial PDA is required to meet conditions above a predetermined level to endure an industrial environment other than a general environment unlike a general PDA. For example, it is absolutely predictable that the industrial PDA may be used in a refrigerated warehouse at 10 or less degrees below zero or may be used outdoors for a long time, unlike the general PDA. Further, the industrial PDA has to have shock resistance, water-resistant property, heat-resisting property/cooling function, etc. above a predetermined level to raise competitiveness as a product since a postman or the like user may carelessly handle it on business. Thus, it is essential that the industrial PDA has to not only be stronger and harder than the general PDA but also have the water-resistant property to keep out rain and snow. However, the outer appearance of the industrial PDA is considerably larger than that of the general PDA since it is designed to have a structure for satisfying the foregoing conditions such as shock resistance, water-resistant property, heat-resisting property/cooling function, etc. above a predetermined level and has to be mounted with a barcode scanner or the like as described above. Therefore, it is needed to reduce the size of the PDA so as to be conveniently used by Asians who have a smaller hand than Westerners.
Meanwhile, among conventional mobile terminals, the industrial PDA includes a keypad with a plurality of key buttons. Through the key buttons, it is possible to carry out writing work such as various messages and memo as well as a telephone call.
At this time, the keypad should not be easily broken down or malfunction due to water, moisture or the like. Therefore, the mobile terminal such as the industrial PDA has to prevent water from entering a keypad area and causing the breakdown or malfunction of the keypad. Of course, convenient assembly and easy maintenance are essential.
However, in the conventional mobile terminal, and particularly in the industrial PDA, the keypad is mostly assembled without any water-resistant structure. Although the keypad has a water-resistant structure, its structure is not only complicated but also uneasy to be manufactured and assembled. Since such a complicated structure and difficulty in the manufacture and assembly increase a production cost undesirably.